1. Field of the Invention
The present invention relates to a display panel including a light emitting element and a display device including the display panel.
2. Description of the Related Art
Recently, in the field of a display device displaying an image, a display device using a current drive type optical element whose light emission luminance changes in accordance with the value of a flowing current, for example, an organic EL (electroluminescence) element as a light emitting element of a pixel has been developed and progressively commercialized. Unlike a liquid crystal element and the like, the organic EL element is a self-luminous element. Thus, a light source (backlight) is unnecessary in the display device using the organic EL element (organic EL display device), and this enables thinning and high luminance of the display device in comparison with a liquid crystal display device in which the light source is necessary. In particular, in the case where the active matrix method is employed as a driving method, it is possible to light and hold each pixel, and it is possible to realize low power consumption. Thus, the organic EL display device is expected to become the mainstream of a flat panel display in the next generation.
However, in the organic EL element, there is an issue that the element is deteriorated in accordance with a fed current value, and the luminance is reduced. Therefore, in the case where the organic EL element is used as a pixel in the display device, there is a case where the state of deterioration is different in each pixel. For example, in the case where information of time, a display channel, or the like is displayed at high luminance in the same position for a long time, deterioration of only the corresponding pixel is rapid. As a result, in the case where a video having high luminance is displayed in a part including the pixel whose deterioration is rapid, the phenomenon called “burning” in which the display is dark only in the part of the pixel whose deterioration is rapid is generated. Since the burning is irreversible, when the burning once occurs, the burning is not eliminated.
A large number of methods to prevent the burning have been proposed so far. For example, in Japanese Unexamined Patent Publication No. Hei 11-26055, such a method is disclosed that images continuously and fixedly displayed are inverted at a predetermined interval, or are shifted to be displayed. In Japanese Unexamined Patent Publication No. 2002-351403, the method is disclosed where a dummy pixel is provided in a region other than a display region, the deterioration degree of the dummy pixel is estimated by detecting a terminal voltage when the dummy pixel emits light, and a video signal is corrected by utilizing the estimation.